Protein Secondary Structure Research Articles

Rapid Quantification of Protein Secondary Structure Composition from a Single Unassigned 1D 13C Nuclear Magnetic Resonance Spectrum.

The function of a protein is predicated upon its three-dimensional fold. Representing its complex structure as a series of repeating secondary structural elements is one of the most useful ways by which we study, characterize, and visualize a protein. Consequently, experimental methods that quantify the secondary structure content allow us to connect a protein's structure to its function. Here, we introduce an automated gradient descent-based method we refer to as secondary-structure distribution by NMR that allows for rapid quantification of the protein secondary structure composition of a protein from a single, 1D 13C NMR spectrum without chemical shift assignments. The analysis of nearly 900 proteins with known structure and chemical shifts demonstrates the capabilities of our approach. We show that these results rival alternative techniques such as FT-IR and circular dichroism that are commonly used to estimate secondary structure compositions. The resulting method requires only the primary sequence of the protein and its referenced 13C NMR spectrum. Each residue is modeled in an ensemble of secondary structures with percentage contributions from random coil, α-helix, and β-sheet secondary structures obtained by minimizing the difference between a simulated and experimental 1D 13C NMR spectrum. The capabilities of the method are demonstrated as applied to samples at natural abundance or enriched in 13C, acquired by either solution or solid-state NMR, and even on low magnetic field benchtop NMR spectrometers. This approach allows for rapid characterization of protein secondary structure across traditionally challenging to characterize states including liquid-liquid phase-separated, membrane-bound, or aggregated states.

CHANGES IN SECONDARY STRUCTURE OF PROTEIN IN SKELETAL MUSCLE DUE TO HIGH-CARBOHYDRATE OR HIGH-FAT DIETS

Objective: Obesity, which arises from changes in lifestyle and feeding habits, is a threat to human health. One essential contributor to the increase in obesity rates is the popularity of high-calorie diets. This study aims to investigate high-fat (HFD) and high-carbohydrate (HCD) diet-induced molecular changes in protein secondary structure in longissimus dorsi skeletal muscle tissues of female inbred C57BL/6J mice by utilizing Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. Materials and Methods: Mice were fed a control diet, HCD, or HFD for 24 weeks. Their skeletal muscle tissues were collected, and their spectra were recorded using a Bruker Invenio S ATR-FTIR spectrometer in the 4000-400 cm-1 region. Results: The protein secondary structure profiles of the HCD group demonstrated a significant rise in antiparallel β-sheet and β-turn and a decline in parallel β-sheets together with the insignificant increase in aggregated β-sheets and a decrease in α-helix. The impact of an HFD on protein conformation is less pronounced than HCD. The HFD diet led to an increase in antiparallel β-sheets and a decrease in parallel β-sheets. Although it was not significant, an increase was observed in β-turn and α-helix. Conclusion: These results propose the appearance of protein aggregation and/or formation of protein-protein intermolecular interaction in skeletal muscle tissues of female inbred C57BL/6J mice. Collectively, these data suggest that both high-calorie diets impair secondary structures of protein in skeletal muscle that may affect its metabolic function.

Bio-spectroscopic analysis of corneal structural alterations in dry eye disease: A study of collagen, co-enzymes, lipids, and proteins with emphasis on phytotherapy intervention

Dry eye disease (DED) stands as a prevalent cause for ophthalmology consultations, securing the third position following refractive errors and cataracts. Moreover, the likelihood of experiencing DED escalates with advancing age. In this experimental study corneal tissue alterations due to DED were investigated over different periods by applying both infrared and synchronous fluorescence spectroscopy. The potential effects of instillation of pomegranate and green tea water extracts as green-friendly treatment modalities were also evaluated. The obtained results collectively indicate that DED affects the OH bearing constituents (collagen, glycosaminoglycans, and proteoglycans) of cornea leading to changes in protein secondary structure and the collagen fibrils. Additionally, enhanced dehydrated environment, and reduced energetic/metabolic state, as indicated by co-enzymes, was observed. Phyto-therapeutic administration can contain these alterations with enhanced energetic/metabolic state and increased hydration environment. In conclusion, instillation of green tea extract can protect/restore the collagen fibrils and its potential effects, in general, exceeds that of pomegranate extract.

Expression of Cystathionine-β-Synthase (CBS) Genes in Grape under Various Abiotic Stresses and Subcellular Localization of VvCBS27

The cystathionine-β-synthase (CBS) domain is present in the proteins of all living organisms and functions as an energy sensor, regulating protein activity through the binding capacity of its adenosine ligands. The role of the CBS gene in plant growth and development, as well as tolerance to abiotic stresses, remains largely unknown, especially in grapevine. In our study, 32 members of the CBS gene family were obtained that were distributed on 15 chromosomes. The results of the structural and evolutionary tree analyses indicated that the VvCBS gene family exhibits diverse intron-exon patterns and highly conserved motifs. Furthermore, the phylogenetic classification of the VvCBS genes revealed the presence of three subfamilies. Subcellular localization analyses showed that the VvCBS genes are mainly located in the plasma membrane region. The secondary structure of the VvCBS protein mainly consists of α-helices, extended strands, β-turns, and random coils. The VvCBS gene family exhibited four co-linear gene pairs, while the numbers for Arabidopsis thaliana and rice were 21 and 7, respectively. The promoter cis-acting element analysis revealed the presence of light-responsive, hormone-responsive, stress-responsive, and growth- and development-related elements in the VvCBS family. The expression characterization demonstrated that 12 VvCBS genes exhibited high expression levels in all grape tissues. Additionally, the RT-qPCR expression analyses showed that the 32 VvCBS exhibited different responses to a variety of abiotic stresses (cold, drought, salt), suggesting that they were functionally differentiated. VvCBS27 was cloned from ‘Pinot Noir’ of grapevine with a coding sequence of 624 bp. Subcellular localization showed that VvCBS27 protein was mainly located in the cytoplasm, cell membrane, and nucleus. This study lays a foundation for elucidating the function of grape CBS protein.

Revealing synergistic mechanisms of biochar-assisted microbial electrolysis cells in enhancing the anaerobic digestion performance of waste activated sludge: Extracellular polymeric substances characterization, enzyme activity assay, and multi-omics analysis

Although biochar (BC)-assisted microbial electrolysis cells (MEC) has been shown to improve anaerobic digestion (AD) performance of waste activated sludge (WAS), the underlying mechanisms remain unclear. This study conducted an in-depth investigation into the mechanism based on analyses of extracellular polymeric substances (EPS) characteristics, enzyme activities and multi-omics. The results showed that compared with the control group, methane production improved by 16.73 %, 21.32 %, and 29.37 % in the BC, MEC, and BC-assisted MEC (BC-MEC) groups, respectively. The reconfiguration of the protein secondary structure increased the hydrophobicity of the EPS, thereby promoting microbial aggregation. In addition, partial least-squares path modeling (PLS-PM) and mantel test based on the enzyme activity and multi-omics analyses revealed that the promotional effect of MEC on the hydrolysis of WAS was superior to that of BC, while BC was more advantageous in promoting electron transfer and biofilm formation regulated by quorum sensing. The synergistic effects of BC and MEC were exemplified in the BC-MEC group. g_norank_Aminicenantales responsible for the hydrolysis of WAS was enriched (29.6 %), and the activities of hydrolytic enzymes including α-glucosidases and proteases were increased by 29.1 % and 43.6 %, respectively. Further, the expressions of genes related to acyl homoserine lactones (AHLs) and diffusible signal factor (DSF) in quorum sensing systems, as well as the genes related to hydrogenase involved in electron transfer (mbhJKL, hyfB-JR, hypA-F, and hoxFHUY), were up-regulated in the BC-MEC group. This facilitated electron transfer and microbial communication, consequently enhancing methane production. This research significantly advances the understanding of the mechanism by which BC-assisted MEC enhances AD performance and provides valuable insights into strategies for improving energy recovery from WAS.

Construction waste as a filler of denitrification biofilter for nitrate utilization from wastewater: Characteristics, performance, microbial community and soilless culture

Construction waste (CW) is produced in large quantities, resulting in severe land occupation and resource depletion. This study utilized CW as fillers to construct a denitrification biofilter (DNBF-CW) for treating secondary effluent from wastewater plants. Performance and mechanism were analyzed by water quality, biomass and its distribution, physicochemical characteristics, microbial community structure, extracellular polymeric substances and protein secondary structure analysis. Results indicated that DNBF-CW achieve NO3−-N and chemical oxygen demand (COD) removal efficiencies (RE) of 97 % and 70 %. The β-sheet of DNBF-CW increased from 47 % to 58 %, accompanied by decrease in random curls from 22 % to 0. Post-use CW showed potential as soilless cultivation substrates, boosting germination rates by 42 ± 7 %. Mechanism investigations elucidated that ZX3 improved efficiency by modulating microbial community composition, with Pseudomonas reaching 37 %. This study shows the multiple use of construction waste, which presents a novel, efficient, and eco-friendly solution for water treatment.

Mutation/metal deficiency in the "electrostatic loop" enhanced aggregation process in apo/holo SOD1 variants: implications for ALS diseases

Despite the many mechanisms it has created to prevent unfolding and aggregation of proteins, many diseases are caused by abnormal folding of proteins, which are called misfolding diseases. During this process, proteins undergo structural changes and become stable, insoluble beta-sheet aggregates called amyloid fibrils. Mutations/disruptions in metal ion homeostasis in the ALS-associated metalloenzyme superoxide dismutase (SOD1) reduce conformational stability, consistent with the protein aggregation hypothesis for neurodegenerative diseases. However, the exact mechanism of involvement is not well understood. Hence, to understand the role of mutation/ metal deficiency in SOD1 misfolding and aggregation, we investigated the effects of apo/holo SOD1 variants on structural properties using biophysical/experimental techniques. The MD results support the idea that the mutation/metal deficiency can lead to a change in conformation. The increased content of β-sheet structures in apo/holo SOD1 variants can be attributed to the aggregation tendency, which was confirmed by FTIR spectroscopy and dictionary of secondary structure in proteins (DSSP) results. Thermodynamic studies of GdnHCl showed that metal deficiency/mutation/intramolecular S–S reduction together are required to initiate misfolding/aggregation of SOD1. The results showed that apo/holo SOD1 variants under destabilizing conditions induced amyloid aggregates at physiological pH, which were detected by ThT/ANS fluorescence, as well as further confirmation of amyloid/amorphous species by TEM. This study confirms that mutations in the electrostatic loop of SOD1 lead to structural abnormalities, including changes in hydrophobicity, reduced disulfide bonds, and an increased propensity for protein denaturation. This process facilitates the formation of amyloid/amorphous aggregates ALS-associated.

Gallium Uncouples Iron Metabolism to Enhance Glioblastoma Radiosensitivity.

Gallium-based therapy has been considered a potentially effective cancer therapy for decades and has recently re-emerged as a novel therapeutic strategy for the management of glioblastoma tumors. Gallium targets the iron-dependent phenotype associated with aggressive tumors by mimicking iron in circulation and gaining intracellular access through transferrin-receptor-mediated endocytosis. Mechanistically, it is believed that gallium inhibits critical iron-dependent enzymes like ribonucleotide reductase and NADH dehydrogenase (electron transport chain complex I) by replacing iron and removing the ability to transfer electrons through the protein secondary structure. However, information regarding the effects of gallium on cellular iron metabolism is limited. As mitochondrial iron metabolism serves as a central hub of the iron metabolic network, the goal of this study was to investigate the effects of gallium on mitochondrial iron metabolism in glioblastoma cells. Here, it has been discovered that gallium nitrate can induce mitochondrial iron depletion, which is associated with the induction of DNA damage. Moreover, the generation of gallium-resistant cell lines reveals a highly unstable phenotype characterized by impaired colony formation associated with a significant decrease in mitochondrial iron content and loss of the mitochondrial iron uptake transporter, mitoferrin-1. Moreover, gallium-resistant cell lines are significantly more sensitive to radiation and have an impaired ability to repair any sublethal damage and to survive potentially lethal radiation damage when left for 24 h following radiation. These results support the hypothesis that gallium can disrupt mitochondrial iron metabolism and serve as a potential radiosensitizer.

Comprehensive bioinformatics assessments of the ROP34 of Toxoplasma gondii to approach vaccine candidates

IntroductionRhoptries proteins (ROPs) are crucial throughout different stages of the Toxoplasma gondii (T. gondii) lifecycle, playing key roles in both the invasion of host cells and their subsequent survival. ROP34 is particularly noteworthy as it significantly influences host gene expression and aids in the transition from the tachyzoite to the bradyzoite form.Materials and methodsThis research utilized various bioinformatics tools to assess physico-chemical properties, allergenic and antigenic characteristics, sites for post-translational modifications (PTMs) and protein's secondary and three-dimensional structures of the ROP34 protein. Furthermore, the study identified potential B-cell, MHC-binding, and cytotoxic T-lymphocyte (CTL) epitopes within the ROP34 sequence.ResultsThe ROP34 peptide comprised 553 amino acid residues, with a calculated average molecular weight (MW) of 61.60149 kDa, an aliphatic index of 73.98, and a GRAVY score of − 0.554. The antigenicity of the multi-epitope peptide was estimated to be 0.526563 and 0.6025 by the ANTIGENpro and VaxiJen servers, respectively, suggesting ROP34 as an immunogenic protein with no allergenic potential. Secondary structure analysis revealed a composition of 52.80% random coil, 36.17% alpha helix, and 11.03% extended strand. The Ramachandran plot for the refined model depicted that 97.46% of the residues were situated in the favored region.ConclusionThis in silico research serves as a foundation for designing effective immunization tactics to target toxoplasmosis. The present article lays the groundwork for future studies and offers perspectives for the advancement of an appropriate toxoplasmosis vaccine.Graphical

Microplastics in freshwater food chains: Priority list based on identification of oxidative stress response characteristic

Exogenous exposure to high concentrations of microplastics (MPs) cause oxidative damage to freshwater food chains (FFCs). Thus, the patterns and mechanisms of oxidative stress responses (OSRs) induced by MPs in FFC organisms were investigated using theoretical simulation methods. Results showed an increasing (reduced) OSR was found in lower trophic levels (higher trophic levels). Besides, polycarbonate (polyvinyl chloride) causes the most (least) significant OSRs in FFC organisms, respectively. The impacts of MP additives were also analyzed using the full factorial experimental design, revealing flame retardants significantly influence oxidative stress variability. A constructive solution of "restriction-control-focus" is proposed for different types of MPs by the coefficient of variation-corrected CRITIC and the nested mean classification method. The mechanism analysis revealed a positive correlation between protein secondary structure orderliness and OSRs. Proteins in organisms that contain a high proportion of hydrophobic non-polar amino acids are more likely to bind to MP and enhance OSRs. This is the first study assessing the OSR patterns and ecological risks of MPs and their additives in FFCs with a proposed priority list, providing theoretical support for risk assessments and management strategies in freshwater environments.

Deep‐eutectic‐solvent‐assisted hydrothermal carbonization of sewage sludge for green wood bioadhesive production

AbstractThis study reports the use of deep‐eutectic‐solvent‐ (DES‐) assisted hydrothermal carbonization (HTC) to disrupt the floc structure of sewage sludge (SS) for deep carbonization, with the resulting hydrochars employed in the preparation of formaldehyde‐free plywood bioadhesives. Sewage‐sludge‐based bioadhesive exhibits an excellent wet shear strength, complying with the requirements of Chinese national standard GB/T 9846–2015 (≥0.7 MPa). The molecular weight of proteins and the formation of covalent bonds via dehydration have a notable role in improving adhesive performance (wet shear strength). The Maillard reaction is a key reaction during HTC to destroy the secondary structure of proteins, resulting in the release of more OH and NH2. The main reaction during hot‐press treatment is dehydration. High ash content in bioadhesives improves flame resistance potential, particularly on addition of DES. A plausible mechanism is proposed for this. This work provides a new method for the valorization of SS‐derived hydrochars and contributes to the development of greener formaldehyde‐free wood bioadhesives.

Comparison of different colored barley hordein/glutelin techno-functional and its ratio modulation on the improvement of reconstituted dough's dynamic thermal processing behavior: A mechanistic investigation

Aiming to boost the high-value utilization of colored barley resources and to broaden its processing depth in cereal products. This study compared the techno-functional characteristics of hordein/glutelin, a key component for gluten in white (W), blue (B), and black (BK) barley, and attempted to modulate their ratios for enhancing reconstituted dough thermal processing suitability. Results indicated that white barley's hordein/glutelin techno-functional profiles are more adapted for dough processing. During dough thermal processing, C2-C3 interval changes were mainly reflected in morphological structure, water distribution, rheological behavior, and textural properties, while the C3-C4 interval variations were interpreted as protein secondary/tertiary structural transitions and intermolecular interactions. Notably, “hordein: glutelin = 50:50″ was a crucial factor in determining the barley dough quality, i.e., low hordein ratio (25:75) was unfavorable for gluten matrix and continuous network formation, whereas its excessive ratio (75:25) weakened the protein aggregation behavior and gluten interaction with starch. Correlation analysis showed that the gluten network's connection density/porosity, protein's secondary structure, and ionic bond strength are key factors modulating dough processing suitability. Therefore, by rationally regulating the hordein/glutelin ratio, barley dough products can be produced with various edible characteristics for consumption. Also, attention should be focused on breeding high hordein ratio barley kernels to improve their gluten profile and thus promote its potential application in cereal processing.

Strategy for improving circular dichroism spectra deconvolution accuracy for macrocyclic peptides in drug discovery

Peptide therapeutics have emerged as an appealing modality in the pharmaceutical industry. Understanding peptide conformation in solution remains one of the most critical areas for peptide drug development. Circular dichroism (CD) spectroscopy is a useful technique to study the secondary structure of proteins and peptides, but the current approaches are limited to protein-focused models to predict high-order structures of peptides, and the models were built based on X-ray crystallography instead of solution-based technique, as a result, such models may have poor predictions for peptides. In this study, we present a novel CD deconvolution model to determine peptide conformation in solution. To quantitatively obtain secondary structure information using CD, a calibration model is needed beforehand to establish the relationship between each secondary structure feature and the corresponding CD response. A reference set containing the majority of cyclic peptides with known structures from solution-state NMR spectroscopy was used to build the calibration model for CD deconvolution. Improved prediction accuracy on the secondary structure determination for cyclic peptides was achieved by this model compared to the commercial standard model using commercially available platforms. This new CD deconvolution method is crucial for peptide conformational analysis in solution, and has the potential to greatly accelerate peptide drug candidate optimization in the pharmaceutical drug discovery field.

Insight into the mechanism on nano fish bone improving the quality of marinated snakehead fish slices during freeze-thaw cycles

The effects of marinating with nano fish bone (NFB) on the physicochemical characteristics and quality of snakehead fish slices during freeze-thaw cycles (1, 3, 5, 7, and 9) were investigated. The highest alterations in surface hydrophobicity, carbonyl content and secondary structure of the slice myofibrillar protein, integrity of cellular structure, and slice quality (whiteness, thawing loss, cooking loss, and sensory) were found in the sample without cryoprotectant (Ck), followed by the sample with commercial cryoprotectant of polyphosphates (PPS), and the lowest in the NFB sample. Comparatively, more moisture but less free water was observed in the NFB sample during the freeze-thaw cycles. Furthermore, NFB surrounded the oil droplet to form a Pickering emulsion, resulting in the stabilization of oil in the marinade. The results indicated that NFB can serve as a potential alternative to commercial cryoprotectant in frozen fish slices, which is attributed to its antifreeze and antioxidant functionalities.

Spatial variability of cake layer in membrane fouling of full-scale MBR: New insights and implications

The spatial variability of the cake layer formed on the hollow fiber membranes during the operation of a full-scale membrane bioreactor (MBR) has been thoroughly investigated, samples from the bulk phase of the reactor and cakes formed on the membrane surface with different locations (i.e., inner layer of the cake (Cake-I), central layer of the cake (Cake-C), and outer layer of the cake (Cake-O)) were collected. The results showed that the viscous nature of proteins, the main component of extracellular polymeric substances (EPS),as well as the hydrophobicity of the protein secondary structure, were factors that led to variations in particle size (Cake-I = 566 μm > Cake-C = 283 μm > Cake-O = 92.2 μm > Bulk sludge = 59.7 μm) and total interaction energy (Cake-I = −216.39 × 104 KT > Cake-C = −68.35 × 104 KT > Cake-O = −30.42 × 104 KT > Bulk sludge = −30.08 × 104 KT) between the spatially varying cake layers. Numerous filamentous bacteria were found in the MBR, and genes related to membrane plugging processes (such as polysaccharide synthesis, surface attachment, and amino acid degradation) of the microbial community composition were regulated within the cake layers. These new insights could be beneficial to developing fouling control and membrane cleaning strategies.

Impact of Multi-Factor Features on Protein Secondary Structure Prediction.

Protein secondary structure prediction (PSSP) plays a crucial role in resolving protein functions and properties. Significant progress has been made in this field in recent years, and the use of a variety of protein-related features, including amino acid sequences, position-specific score matrices (PSSM), amino acid properties, and secondary structure trend factors, to improve prediction accuracy is an important technical route for it. However, a comprehensive evaluation of the impact of these factor features in secondary structure prediction is lacking in the current work. This study quantitatively analyzes the impact of several major factors on secondary structure prediction models using a more explanatory four-class machine learning approach. The applicability of each factor in the different types of methods, the extent to which the different methods work on each factor, and the evaluation of the effect of multi-factor combinations are explored in detail. Through experiments and analyses, it was found that PSSM performs best in methods with strong high-dimensional features and complex feature extraction capabilities, while amino acid sequences, although performing poorly overall, perform relatively well in methods with strong linear processing capabilities. Also, the combination of amino acid properties and trend factors significantly improved the prediction performance. This study provides empirical evidence for future researchers to optimize multi-factor feature combinations and apply them to protein secondary structure prediction models, which is beneficial in further optimizing the use of these factors to enhance the performance of protein secondary structure prediction models.

A Biophysical Study of Molecular Interaction of Tucatinib with Bovine Serum Albumin

AbstractA profound understanding of the binding dynamics of drugs with plasma proteins is highly important as it determines its therapeutical potential. Herein, we have investigated the molecular interaction of Tucatinib (TUC), a novel, primitive and highly selective drug for treatment of HER2+ advanced unresectable breast cancer, with bovine serum albumin (BSA) using multi‐pronged spectroscopic techniques and molecular docking. TUC considerably quenched the intrinsic fluorescence of BSA via static quenching mechanism, and it binds to the hydrophobic cleft of subdomain IIA of BSA with a moderate binding affinity. The thermodynamic analysis revealed the major interplay of van der Waals forces and hydrogen bonding interactions in stabilising the binding. The Förster distance ‘r’ signifies feasible energy transfer between BSA and TUC. The conformational analyses indicate some alterations in the protein secondary structure as a consequence of some changes in the protein polar environment due to complex formation. The experimental results are supported by docking analyses.

Evaluation of the water state and protein characteristics of Tibetan pork under the storage conditions of modified atmosphere packaging: Effect of oxygen concentration

To explore the changes in water status and protein characteristics of Tibetan pork (TP) under modified atmosphere packaging (MAP) with different oxygen concentrations compared to Duroc×Landrace×Yorkshire pork (DLY), the water holding capacity (WHC), water distribution, protein oxidation, and conformation of both types were determined. Results indicate that under MAP, TP pork and DLY pork exhibited higher water retention and lower protein oxidation compared to air packaging. However, with increased oxygen concentration in the MAP, protein oxidation intensified, leading to reduced WHC in the pork. Compared to DLY pork, TP pork in different packaging conditions maintained the integrity of protein secondary and tertiary structures, reducing protein cross-linking aggregation. The lower content of P3 in the two-dimensional relaxation spectra, shorter T1 and T2 relaxation times, and higher proton density suggest better water retention properties in Tibetan pork. These findings support the development of long-distance preservation and transportation technologies for TP pork.

High-intensity ultrasound-modified Jerusalem artichoke leaf protein for stabilizing corn oi-in-water emulsion and Enhacing curcumin delivery

Jerusalem artichoke leaf protein (JALP) has limited applications because of its dark color, even though Jerusalem artichoke is a cash crop. This study utilized high-intensity ultrasound (HIUS) (≤ 600 W) to modify the physicochemical characteristics and functional properties of JALP. Compared with the JALP, all the HIUS-treated JALP (UJALP) samples had a lighter brown color, higher absolute ζ-potential value, lower Z-average size, higher surface hydrophobicity, higher water solubility, lower turbidity, more -SH group, and higher water-holding, oil-holding, emulsifying and foaming capacities. The HIUS treatment disrupted certain non-covalent and SS bonds, promoted protein depolymerization, change protein secondary structures, causing partial unfolding of protein and exposure of some charged groups, hydrophobic groups and chromophores (like tryptophan and tyrosine). The UJALP-stabilized corn oil-in-water emulsions (UJALPEs) were more stable than the JALP-stabilized emulsion (JALPE). The bioaccessibility of curcumin in the JALPE (56.38 %) was significantly lower than in the UJALPE-600 W (64.59 %).

Characteristics of organic matter driven by Eichhornia crassipes during co-contamination with per(poly)fluoroalkyl substances (PFASs) and microplastics (MPs)

Co-contamination with MPs and PFASs has been recorded, particularly in surface-water environments. Floating macrophyte microcosms are an important part of the surface water ecosystem, and dissolved organic matter (DOM) driven by floating macrophytes (FMDDOM) is critical for maintaining material circulation. However, knowledge gaps remain regarding the impact of MPs and PFASs co-pollution on FMDDOM. An greenhouse simulation experiment was conducted in this study to investigate the effects of four PFASs, perfluorooctanoic acid (PFOA), perfluoro-octane-sulfonic acid (PFOS), perfluoro-2-methyl-3-oxahexanoic acid (Gen X), and potassium 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate (F-53B), on FMDDOM sourced from Eichhornia crassipes (E. crassipes), a typical floating macrophyte, in the presence and absence of polystyrene (PS) MPs. Four PFASs increased FMDDOM release from E. crassipes, leading to a 32.52–77.49 % increase in dissolved organic carbon (DOC) levels. PS MPs further increased this, with results ranging from −21.28 % to 26.49 %. Based on the parallel factor analysis (PARAFAC), FMDDOM was classified into three types of fluorescent components: tryptophan-like, humic-like, and tyrosine-like compounds. Contaminants of MPs and PFASs modified the relative abundance of these three components. Protein secondary structure analysis showed that fluorocarbon bonds tended to accumulate on the α-helix of proteins in FMDDOM. The relative abundance of fluorescent and chromophorous FMDDOMs varied from 0.648 ± 0.044 to 0.964 ± 0.173, indicating that the photochemical structures of the FMDDOM were modified. FMDDOM exhibits decreased humification and increased aromaticity when contaminated with MPs and PFASs, which may be detrimental to the geochemical cycling of carbon. This study offers a theoretical basis for assessing the combined ecological risks of MPs and PFASs in floating macrophyte ecosystems.